The application of luminescence dating to aeolian sands in desert regions has revolutionized our understanding of the dynamics of these systems on centennial to millennial time scales. The availability of increasingly precise numerical ages for periods of aeolian deposition has provided information on rates of dune migration and accumulation of sand and supported new models of dune development. When combined with information on dune stratigraphy and morphology, clustering of luminescence ages shows that most dunefields and many large dunes are composite features that have developed as a result of multiple periods of aeolian construction separated by periods of non-deposition or erosion. Numerical ages have enabled identification of the timing and duration of these periods of aeolian activity and facilitated understanding of the conditions in which they occurred via correlation with other sources of palaeoenvironmental proxy data. The result is a much-enhanced conceptual and empirical understanding of how desert dunes and sand seas have responded to Quaternary changes in climate and sea level, manifested by changes in sediment supply, availability and mobility.